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Subject[PATCH 1/2] pipe: fix race with fcntl
Date
Fix other long standing issues caused by fcntl(,F_SETFL,):
- User can disable O_DIRECT for pipe[1] (paketized IO), but can not enable it again.
- Currently we do not set O_APPEND on pipe[1] (IMHO it is wrong, but let it be)
so it is reasonable to completely prohibit change O_APPEND flag on both
end's of pipe. Add ->check_flags method in order to diallow O_APPEND toggling.

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
---
fs/fcntl.c | 6 ++++--
fs/pipe.c | 16 +++++++++++++---
2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/fs/fcntl.c b/fs/fcntl.c
index ee85cd4..0bdc9c7 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -51,9 +51,11 @@ static int setfl(int fd, struct file * filp, unsigned long arg)
if (arg & O_NDELAY)
arg |= O_NONBLOCK;

+ /* allowed only for inodes with ->direct_io method or write pipe */
if (arg & O_DIRECT) {
- if (!filp->f_mapping || !filp->f_mapping->a_ops ||
- !filp->f_mapping->a_ops->direct_IO)
+ if ((!filp->f_mapping || !filp->f_mapping->a_ops ||
+ !filp->f_mapping->a_ops->direct_IO) &&
+ !(get_pipe_info(filp) && (filp->f_flags | O_WRONLY)))
return -EINVAL;
}

diff --git a/fs/pipe.c b/fs/pipe.c
index 8865f79..0c15647 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -329,9 +329,9 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
return ret;
}

-static inline int is_packetized(struct file *file)
+static inline int is_packetized(struct kiocb *iocb)
{
- return (file->f_flags & O_DIRECT) != 0;
+ return (iocb->ki_flags & IOCB_DIRECT) != 0;
}

static ssize_t
@@ -427,7 +427,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
buf->offset = 0;
buf->len = copied;
buf->flags = 0;
- if (is_packetized(filp)) {
+ if (is_packetized(iocb)) {
buf->ops = &packet_pipe_buf_ops;
buf->flags = PIPE_BUF_FLAG_PACKET;
}
@@ -943,6 +943,15 @@ err:
return ret;
}

+/* XXX: Currently it is not possible distinguish read side from write one */
+static int pipe_check_flags(int flags)
+{
+ if (flags & O_APPEND)
+ return -EINVAL;
+
+ return 0;
+}
+
const struct file_operations pipefifo_fops = {
.open = fifo_open,
.llseek = no_llseek,
@@ -952,6 +961,7 @@ const struct file_operations pipefifo_fops = {
.unlocked_ioctl = pipe_ioctl,
.release = pipe_release,
.fasync = pipe_fasync,
+ .check_flags = pipe_check_flags,
};

/*
--
1.7.1


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